It is well known that alpha,beta-olefinically unsaturated compounds may be prepared by carbonylating acetylenically unsaturated compounds with hydroxyl-containing compounds. The type of alpha,beta-olefinically unsaturated compound obtained depends upon the type of hydroxyl-containing compound used. Thus, if a carboxylic acid is used, the product is a carboxylic anhydride; if an alcohol is used, the product is a carboxylic ester; and if water is used, the product is a carboxylic acid. For example, the commercially important monomer, methyl methacrylate, may be prepared by carbonylating propyne with methanol.
One process for the preparation of alpha,beta-olefinically unsaturated compounds is disclosed in European Patent No. EP-A1-0186228. The process comprises reacting an acetylenically unsaturated compound with carbon monoxide and water or an alcohol in the presence of a catalyst system formed by combining a palladium (II) compound, an organic phosphine and a non-halogenic acid. It is apparent from the Examples in the patent specification that this process proceeds with a good reaction rate and good selectivity.
European Patent No. EP-A2-0271144 also discloses a process for the preparation of alpha,beta-olefinically unsaturated compounds. The process comprises reacting an acetylenically unsaturated compound with carbon monoxide and a hydroxyl-containing compound in the presence of a catalyst system comprising a palladium compound, a protonic acid and an organic monophosphine having three aromatic substituents at least one of which contains a nitrogen atom. The processes exemplified in the patent specification proceed with a very high reaction rate and high selectivity.
It has now been found that alpha,beta-olefinically unsaturated compound may be prepared with a good reaction rate and high selectivity using a particular organic diphosphine.